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Work Step by Step
$K_a=[H_3O^+][NH_3]/[NH_4^+]$ Applying the -log to both sides $pKa=pH-log([NH_3]/[NH_4^+])$ $[NH_3]/[NH_4^+]=1.77$ Mix them with a ratio of 1.77 mol of ammonia per mol of ammonium.
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